The present invention relates to a database management system. In particular, the present invention relates to an object-oriented database management system handling multimedia data such as video data and audio data.
Conventional object-oriented database management systems are described in "The Object Database Standard: ODMG-93" edited by R.G.G. Cattell and published by Morgan Kaufmann Publishers, San Mateo, Calif., and "OBJECT-ORIENTED DATABASES" authored by Setrag Khoshafian and published by John Wiley & Sons, Inc., for example. In an object-oriented database management system, a collection having, as components, data to be subjected to database queries or identification data for referring to those data is defined as object, those objects stored in a nonvolatile storage such as a disk equipment are managed as a database. In the following description, components forming an object are referred to as "contents."
An object is defined as one belonging to a class declaring a configuration of the components.
Declaration of a class is conducted for a class name. For an object belonging to the class, one or more sets each having a type (such as an integer type or character type) of each component and a name identifying the component are declared.
In an object-oriented database management system, an object has identification information for uniquely specifying it. As this identification information, an address value of a storage area storing the object is used, for example.
Retrieval in an object-oriented database management system will now be described. For one or more objects belonging to a certain class, objects containing contents which satisfy given conditions are retrieved. Identification information of an object of a set having identification information of those objects as components is obtained as a.result of the retrieval.
The class to which the object of the set returned as the retrieval result belongs is a class declared as already known by the object-oriented database management system. In addition, its storage area is provided temporarily for each retrieval query.
Furthermore, in an object-oriented database management system having a configuration of a client server system, a database client machine issuing a query sends a query requirement to a database server machine which processes the query and the database server machine conducts processing and thereafter returns a result of the query to the database client machine which issued the query requirement.